Ryu Sihyuk He lost his entire family to a Yomi attack on the day of his university graduation. As a result, he harbors the deepest hatred for them. He was holding out alone in unit 603, but when the Yomi invaded the apartment, he escaped with Sangyoon and has been surviving ever since. He is 25 years old. Three years ago, at age 22, he was a genius dubbed the youngest Doctor of Engineering and the future of science. Accordingly, he is highly skilled with his hands and can improvise various tools necessary for survival. Chef Yu took a liking to this and brought Sihyuk to his base to train him.

Sangyoon Ryu Sihyuk's neighbor, residing in unit 404. In a disaster where everyone has become selfish and looks out only for themselves, Sangyoon remains different and is the closest older-brother figure to Sihyuk. He is 34 years old, older than Ryu Sihyuk. His combat ability is that of an average civilian.

Gordon Ram-G She appears riding a doll made from Yomi corpses. Afterward, she secretly follows Ryu Sihyuk and asks him to kill 'Mother,' the root cause of this incident. Despite her small stature, she possesses immense strength and easily overpowers the human Sihyuk. Her ditsy, squirrel-like appearance is a disguise; her true form is closer to a hideous monster. She is female. She calls Ohwol her older sister. According to Ohwol, she is a traitor who sided with humans. Eventually, Ohwol captures her and brings her before Mother. She is the second child and second daughter among Hyoyi's six siblings.

Ko Hee A platoon leader in the Army's Cockroach Unit with the rank of First Lieutenant. She has known Ryu Sihyuk since childhood. She rescued Kim Hyoeun and brought her to the unit, but Hyoeun was a Yomi disguised as a human, and the entire unit except for Ko Hee was killed. Ko Hee survived alone and fled, only to be attacked by Yomi again, barely surviving with the help of Ji Suyeong, a member of 'Judges of Tomorrow' (J.O.T). Ko Hee decides to train to become stronger and join J.O.T to avenge her fallen comrades. She is likely only 1 or 2 years older than Ryu Sihyuk, as they attended the same high school.

Ji Suyeong The female soldier who rescued Ko Hee. She is the J.O.T Northern Gyeonggi Branch Manager. She is 30 years old and possesses the skills to exterminate Yomi with incredible combat techniques.

Chef Yu The leader of the Water Merchants. He uses a floating restaurant called 'Hangang Love' as his hideout. When the disaster struck, he began catching fish and boiling Han River water, selling it as drinking water under false pretenses. He looks somewhat aged, but his strength is incredible, capable of tearing a Yomi apart with his bare hands. Liking Ryu Sihyuk's special talents, he gives him spicy fish stew and water for free. However, he cannot be called a person of good character as he scams people. Yet, seeing him speak kindly to Ji Suyeong suggests he isn't entirely malicious; he wasn't always this way. He stopped trusting humans after his wife was murdered by ordinary people, not Yomi. As Yomi attacks intensified, he hired Ryu Sihyuk as an assistant. He displays superhuman fighting skills against both Yomi and other humans. Since his daughter's surname is Yu, his surname is obviously Yu.

Yu Yeonju Chef Yu's daughter. She is 21 years old and has a somewhat childish personality. A promising shooting athlete, her marksmanship is excellent, especially with sniper rifles where precision is key. She is quite beautiful. She doesn't resemble her father at all, having inherited her mother's looks exactly.

Oh Happy A member of J.O.T and a Yomi trainer for the resistance combat unit. She employs a method of raising Yomi to catch Yomi. She loves baseball and occasionally talks about it. Though she may seem eccentric, she is a highly capable combatant. She knows the Yomi's weaknesses and seals their abilities by blocking their mouths and ears.

Yomi Adorable bundles of fur and the primary enemy. The name is derived from 'Yogwi' (monster). They are mysterious creatures and monsters that appeared for no apparent reason. Basically, a single individual can easily handle one human. They have incredible reproductive rates, and their skin is squishy, boasting a durability that makes them hard to beat to death. Their most terrifying trait is their cuteness. They use this as a weapon, attacking when people let their guard down, or boasting a level of cuteness that leaves people dazed even when they know these are man-killing monsters. They cry with a 'Um-pyu-pyu' sound. Though they are very cute, as the primary enemy, they are the beings killed most frequently. When they die, pink blood pours out. It is said they smell like grilled tripe when burned, making them the worst existence that torments humans even in death.

Lee Young Another member of the Yomi race disguised as a human. She is Hyoyi's youngest daughter and has an immature side befitting the youngest. However, she has a very cruel streak and is a sadist who enjoys the pain of others. Unlike Ram-G, she possesses the ability to grow Yomi to a giant size.